This invention relates to material handling equipment. It has been developed specifically for the automobile industry for handling parts on a mass production line. However; from what follows, it will be apparent that this has applications in other production areas and is not limited to the production of automobiles or other motor vehicles.
On a production line, such as an automobile parts production line, parts, such as doors, trunk lids, hoods, body panels, etc., are stamped form sheet metal at a press and are produced at the rate, currently, of eight to twenty five per minute. The handling of these parts on the line is largely automated but at the end of the line, the parts are removed manually by crews of workers. The parts are moved into a rack that is mounted on a riser. Usually the parts are placed vertically in slots in a rack and thereafter are moved to a storage location; usually by a fork lift truck for storage before further processing and assembly.
The standard procedure is to provide a table onto which the stamped parts discharge from a conveyor. As the parts arrive at the table they are manually removed then placed in a rack. When a rack is filled, it is moved to a location from which it can be carried by forklift to storage.
Commonly the racks are placed on turntables at the end of the press line. The turntable can rotate from the loading position to an unloading position at which they are picked up by forklift to be moved to a temporary storage location. Thereafter the turntable is rotated to a position at which empty racks can be positioned and then the table is turned to the loading position once more to repeat the cycle.
Currently the turntables are supported by air bearings and are moved to the load, unload and reload rack positions by a mechanical drive. The riser mechanism can be adjusted for height to accommodate the ergonomic requirements of the crew and the geometry of the parts of the plan, but the loads placed on the conveyor are ones, which involve significant and taxing physical effort. While with the air bearing arrangement the loads once moving require little effort but to start these loads and to stop them with accuracy is demanding and inaccurate. Thus it is proposed that the table be mechanically rotated giving accuracy of position and increased speed. The most attractive proposition was using an air motor to assist in turning the table simply because air is abundant and compressors are commonly involved in production line processes. However, simply because compressed air is available, it is not abundant and cheap. Vast amounts are needed to inflate air bearings underneath the bulk of a large table and its load. These applications did not achieve higher index speed and are too expensive to operate and maintain.
In order to achieve enough rigidity for turntables supported on air bearings, it is necessary to have a fairly massive structure to tolerate the vertical loading and achieve smooth operation of the turntable. The rigidity and strength requirements results in turntables being considerably heavier than the present invention. The large mass associated with turntables riding on air bearings results in high inertia conditions that require large amounts of horse power in order to accelerate and decelerate the table to a preselected position.
In addition, in order to provide for the rigidity and strength that is necessary, the tables tend to be very thick which usually means that the turntable is mounted above the normal floor level. Therefore tow motors and/or tractors cannot simply drive onto the turntable, but must take precautions to ensure that any moving vehicles do not bump into the elevated turntable and that the load is carefully placed onto the turntable from a distal position.
It is common to have two or even more turntables receive from a production line with a crew to each turntable. The receiving table being a hexagonal outline with a base receiving from the line, two adjacent sides defining paths to two turntables, two sides facing the turntables and aside opposite the base side which could, conceivably, accommodate a third turntable. The conditions clearly are crowded and, shared by a crew and forklifts are fraught with risk.
The turntables are usually elevated and risers are positioned on them to hold the racks so that the turntables are occupying spaces, which are dedicated to them and are useless for other purposes. To this state of the art comes the inventor/engineer with a dramatic new proposal.
The inventor proposes a new turntable one or more of which can be placed at the end or intermediate location of a production line and which can be moved between a load, unload and reload positions with precision and can be moved to intermediate positions between the load and unload positions to accommodate a crew requirement with precision and safety. To achieve this the inventor uses a disc depending on a central bearing and housed within a peripheral curbing and drive comprising a motor, a drive gear, a chain, or other flexible element trained around a drive gear and the periphery of the disc. The disc has a generally flat top surface and has an annular flange at or adjacent to its periphery about which the chain is trained. The disc and flange together have a height equal to the thickness of the floor finishing layer so that by removal of that layer to expose the sub flooring the, disc can be located with its top surface flush with the surrounding floor. This provides significant safety advantages over existing arrangements and it permits the space the disc occupies to be used for multiple purposes.
With such an arrangement it becomes necessary only to excavate sub floor in a small region to accommodate the drive mechanism.
It is desirable to have a turntable which has low total mass which results in a low total inertia which results in a turntable requiring much less power to accelerate and decelerate efficiently and accurately. Additionally such a turntable has a much lower profile and/or overall thickness resulting in a turntable which in most cases can be mounted flush to the existing floor line due to the shallower profile.
The present invention a material handling turntable comprises:
a) a turntable including a top for receiving a load thereon and a bottom;
b) a means for driving said turntable in circular motion;
c) a bearing means for supporting vertical loading on said turntable operably adapted to slidably interact with said bottom of said turntable.
Preferably wherein said bearing means includes a low friction disc slidably receiving said bottom of said turntable thereon.
Preferably wherein said turntable assembled from multiple pie sections fastened to each other.
Preferably wherein each pie section including a lattice work type frame with the bottom of each frame member defining a bottom load bearing surfaces making sliding contact with said bearing means.
Preferably wherein each frame member including U shaped steel beams laid on their side with one leg of the U shaped channel defining the load bearing surfaces at the bottom.
Preferably wherein each pie section attached to a central hub at one end and to adjacent pie sections at the other broad end.
Preferably wherein each pie section is attached with one locating pin to the central hub and with one fastener at each side of the broad end of the pie to each adjacent pie section.
Preferably wherein each pie section fixed in place at three attachment points.
Preferably wherein said drive means including a chain trained around the outer periphery of said turntable which is driven by a sprocket to rotate said table.
Preferably wherein said chain is trained onto a frictional element located on the outer periphery of said turntable for holding said chain in place and imparting rotational forces.
Preferably wherein said low friction disc comprised of ultra high molecular weight polyethylene pad.
Preferably wherein said top including top plates providing for a substantially level loading surface.
Preferably wherein the number and size of pie sections is selected for ease of transportation on a flatbed trailer.
Preferably wherein said drive means including control means for controlling the rotation and positioning accuracy of said turntable.
Preferably wherein said drive means including a feed back drive system with servo motors.
Preferably wherein the turntable including a central precision bearing for supporting any radial forces.